The GTPase IFT27 is involved in both anterograde and retrograde intraflagellar transport.
The GTPase IFT27 is involved in both anterograde and retrograde intraflagellar transport.
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DOI：
10.7554/elife.02419
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发表时间：
2014-04-24
期刊：
影响因子：
7.7
通讯作者：
Bastin P
中科院分区：
文献类型：
--
作者：
Huet D;Blisnick T;Perrot S;Bastin P
纤毛和鞭毛的构建取决于鞭毛内运输 (IFT)，即由特定驱动蛋白和动力蛋白马达驱动的两种蛋白质复合物（IFT-A 和 IFT-B）的双向运动。 IFT-B 和驱动蛋白与顺行运输相关，而 IFT-A 和动力蛋白参与逆行运输。令人惊讶的是，小型 GTPase IFT27（IFT-B 复合体的成员）对于布氏锥虫的逆行货物运输至关重要。我们发现这是由于未能将 IFT-A 复合物和 IFT 动力蛋白导入鞭毛室所致。为了进一步了解 IFT27 的作用，在存在或不存在内源 IFT27 的情况下表达 GDP 或 GTP 锁定版本。 GDP 锁定版本无法进入鞭毛并与其他 IFT-B 蛋白相互作用，并且其唯一表达会阻止鞭毛形成。这些发现表明，需要具有 GTP 酶活性的 IFT27 才能与 IFT 复合物结合，并且 IFT27 在逆行运输机械的货物装载中发挥作用。 DOI：http://dx.doi.org/10.7554/eLife.02419.001 在许多细胞的表面上发现了称为纤毛和鞭毛的长而薄的结构，并发挥一系列作用，包括推动细胞或感知周围环境的变化。鞭毛内运输（简称IFT）的过程负责真核细胞中鞭毛的构建。称为 IFT 序列的蛋白质复合物携带着构成鞭毛的构件，沿着鞭毛基部和尖端之间的微管“轨道”运行。 IFT 列车由两种不同的蛋白质复合物（称为 IFT-A 和 IFT-B）组成，由各种分子马达拖动。 IFT-B 复合体对于列车向鞭毛尖端移动是必需的，因此使鞭毛能够生长。 IFT-A 蛋白复合物需要将序列循环回到鞭毛基部。休特等人。研究了一种名为 IFT27 的蛋白质在鞭毛内运输中的作用。 IFT27 是 IFT-B 复合体的一部分，因此人们认为它只影响鞭毛的生长方式。然而，当 IFT27 缺失时，短鞭毛仍然会生长，但它们充满了无法从尖端反转的 IFT 序列。休特等人。研究表明，如果 IFT27 不存在，则 IFT-A 复合物和使火车倒车所必需的分子马达不会被运输到鞭毛中。因此，这是 IFT-B 蛋白影响 IFT-A 复合物和转运回碱基的不寻常情况。 IFT27 还影响 IFT-B 复合物的形成方式。 ITF27 可以与一些小分子结合，从而可以“打开”或“关闭”蛋白质。休特等人。发现当 IFT27 关闭时，它不会被转运到鞭毛中，也不能与 IFT-B 复合物中的一些其他蛋白质结合。这意味着如果 IFT27 被锁定在非活动状态，则 IFT-B 复合体不会形成，鞭毛也无法生长。因此，需要激活 IFT27 来组装 IFT 序列并确保其沿着微管轨道向任一方向移动。 DOI：http://dx.doi.org/10.7554/eLife.02419.002
The construction of cilia and flagella depends on intraflagellar transport (IFT), the bidirectional movement of two protein complexes (IFT-A and IFT-B) driven by specific kinesin and dynein motors. IFT-B and kinesin are associated to anterograde transport whereas IFT-A and dynein participate to retrograde transport. Surprisingly, the small GTPase IFT27, a member of the IFT-B complex, turns out to be essential for retrograde cargo transport in Trypanosoma brucei. We reveal that this is due to failure to import both the IFT-A complex and the IFT dynein into the flagellar compartment. To get further molecular insight about the role of IFT27, GDP- or GTP-locked versions were expressed in presence or absence of endogenous IFT27. The GDP-locked version is unable to enter the flagellum and to interact with other IFT-B proteins and its sole expression prevents flagellum formation. These findings demonstrate that a GTPase-competent IFT27 is required for association to the IFT complex and that IFT27 plays a role in the cargo loading of the retrograde transport machinery. DOI: http://dx.doi.org/10.7554/eLife.02419.001 Long, thin structures called cilia and flagella are found on the surface of many cells, and perform a range of roles, including propelling the cells around or sensing changes in the surrounding environment. A process called intraflagellar transport (IFT for short) is responsible for flagellum construction in eukaryotic cells. Protein complexes called IFT trains carry the building blocks that make up flagella along microtubule ‘tracks’ between the base and the tip of a flagellum. IFT trains are made from two different protein complexes called IFT-A and IFT-B, which are dragged by various molecular motors. The IFT-B complex is necessary for the train to move towards the tip of the flagellum, and so enables the flagellum to grow. The IFT-A protein complex is required to recycle the train back towards the base of the flagellum. Huet et al. examined the role that a protein called IFT27 plays in intraflagellar transport. IFT27 is part of the IFT-B complex, and so it was thought to only affect how flagella grow. However, short flagella still grow when IFT27 is absent, but they are filled with IFT trains that are not able to reverse back from the tip. Huet et al. reveal that the IFT-A complex and the molecular motor that is essential for reversing the train are not transported into the flagellum if IFT27 is not present. This is therefore an unusual case of an IFT-B protein affecting the IFT-A complex and the transport back to the base. IFT27 also affects how the IFT-B complex forms. ITF27 can bind to some small molecules, which can switch the protein ‘on’ or ‘off’. Huet et al. found that when IFT27 is switched off it is not transported into flagella, and also cannot bind to some of the other proteins in the IFT-B complex. This means that if IFT27 is locked in an inactive state, the IFT-B complex does not form, and a flagellum cannot grow. Therefore, activated IFT27 is needed for putting together the IFT train and to ensure its movement in either direction along the microtubule tracks. DOI: http://dx.doi.org/10.7554/eLife.02419.002